Live virtual server migration between physical servers is a very valuable feature made possible by virtualization. The ability to copy the running state of a virtual server from one physical server to another without dropping existing sessions of the virtual server enables capabilities such as physical server shutdown, localization of virtual servers where the optimal virtual server performance is possible, etc.
For live migration, a virtual server disk image is made accessible to the source and target physical servers. For faster copy of the image and the memory state of the virtual server, a common practice is to deploy a dedicated 1 Gigabit (G) or 10 G link between the physical servers in order to copy the image and/or the memory state from the source physical server to the target physical server.
Once the memory state is migrated, the virtual server does not immediately become active at the new location since while the migration is occurring the state on the server is changing. Therefore, the migration process copies the image at a point in time and then the changes on the source physical server are monitored. These changes are then replicated at the target physical server. The continuous change in state delays the live virtual server migration.